I appreciate what you say, Medusa, but even so I think some of it is unarguable:
1) your banned roads list isn't well-publicised or on your website, I believe. This causes avoidable disappointment and to be honest is my primary gripe with SCS. You can't defend this - it would not be difficult to arrange and would surely save a lot of heartache. You could post the list to this thread, it would be a step forward over where you are currently. Then people would know how you guys felt about them adopting when they live on a busy road, and wouldn't need to waste your valuable time trying to care for animals you don't want them to have!
2) the RSPCA - just for instance - disagrees with your views on busy roads; they have no such list. That doesn't mean they're right and you're wrong, but it is still a fact that there is disagreement among the professionals, never mind the rest of us. It suggests that you might, or might not, have drawn the line in the right place. I respectfully tend to agree with the RSPCA on this one (you'd never have guessed, would you!).
3) if "most" of the cats living wild are feral, then I guess I was speaking about the rest of them! I'm sure you have more non-feral cats than spaces available - or am I wrong about this? Are you the world's only over-funded animal welfare organisation? * I'm sure that can't be the case :-D
Ultimately it still seems a shame to me that you won't place a cat with people who live on a busy road because you "believe that animal is at an unacceptable risk of suffering harm", when other welfare organisations would disagree. It seems a greater shame that you don't publicise this policy more widely.
:edit: "world's only over-funded animal welfare organisation" - I forgot about the Battersea Dogs' Home!